California fires are raging: Get the facts on wildfires

As seasonal winds drive flames across the state, here's what you need to know about how these fires start and how they're put out.

Climate 101: Wildfires

California fires are raging: Get the facts on wildfires

As seasonal winds drive flames across the state, here's what you need to know about how these fires start and how they're put out.

Climate 101: Wildfires

Strong winds are fueling fires across California, with the Kincade Fire in Sonoma County, near San Francisco, among the fiercest reported. Eyewitnesses told local news that the fire was racing through vineyards and across mountains, setting homes ablaze and forcing residents to flee.

In Southern California, the Tick Fire near Santa Clarita is burning out of control, CNN reports, and is moving quickly as seasonal winds gust across the state.

California’s most destructive fires often occur in the autumn, when vegetation has had the long, hot, dry summer to desiccate into perfect tinder, and when the annual offshore winds whip onshore.

California’s worst fires over the past few years, including the Camp Fire and 2017’s Thomas Fire, started when power lines sparked flames in dry grasses. The Los Angeles Times reports that local power lines were still live near the ignition point of the Kincade Fire, which may have sparked the conflagration.

Firefighters will battle the blazes through the weekend as fire officials expect them to grow.

How wildfires start

Wildfires can burn millions of acres of land at rapid speeds and can consume everything—trees, homes, even humans—in their paths. These rolling flames travel up to 14 miles an hour, which converts to about a four-minute mile pace, and can overtake the average human in minutes.

Destruction caused by wildfires in the United States has significantly increased in the last two decades. An average of 72,400 wildfires cleared an average of 7 million acres of U.S. land each year since 2000, double the number of acres scorched by wildfires in the 1990s. In 2015, the largest wildfire season recorded in U.S. history, wildfires burned more than 10 million acres of land.

As much of the U.S. is expected to get hotter and drier with climate change, wildfire risk is generally expected to rise. At the same time, as the human population rises and people keep moving into rural and wilderness areas, more homes and other structures are likely to be placed in harm’s way.

Though they are classified by the Environmental Protection Agency as natural disasters, only ten to 15 percent of wildfires occur on their own in nature. The other 85 to 90 percent result from human causes, including unattended camp and debris fires, discarded cigarettes, and arson.

Naturally occurring wildfires can spark during dry weather and droughts. In these conditions, normally green vegetation can convert into bone-dry, flammable fuel; strong winds spread fire quickly; and warm temperatures encourage combustion. With these ingredients, the only thing missing is a spark—in the form of lightning, arson, a downed power line, or a burning campfire or cigarette—to wreak havoc.

Natural or man-made, three conditions must be present for a wildfire to burn: fuel, oxygen, and a heat source. Firefighters call these three elements the fire triangle.

Fuel is any flammable material surrounding a fire, including trees, grasses, brush, even homes. The greater an area's fuel load, the more intense the fire is likely to be. The most wildfire-prone state is California, which lost 1,823,153 acres of land to 8,054 wildfires in 2018.

Air supplies the oxygen a fire needs to burn. California wildfires are often made worse by the hot, dry Santa Ana winds, which can carry a spark for miles.

Heat sources help spark the wildfire and bring fuel to temperatures hot enough to ignite. Lightning, burning campfires or cigarettes, and even the sun can all provide sufficient heat to spark a wildfire.

Violent infernos are most common in the U.S. West, where heat, drought, and frequent thunderstorms create ripe conditions. Montana, Idaho, Wyoming, Washington, Colorado, Oregon, and California experience some of the worst conflagration. Wildfires also occur around the world and in most of the 50 states.

How they are stopped

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High winds and hot temperatures fanned a 1996 wildfire in the foothills around Boise, Idaho, into an inferno that burned for seven days. When it was finally extinguished, the outbreak—dubbed the Eighth Street Fire—had scorched some 15,000 acres (6,000 hectares) and stripped bare two of the region's major watersheds.

Firefighters battle blazes by depriving them of one or more of the fire triangle fundamentals. Traditional methods include:

  • Water dousing and spraying fire retardants to extinguish existing fires.
  • Working in teams, often called hotshots, to clear vegetation to contain and eventually starve the fire of its fuel. The results are called firebreaks.
  • Controlled burning, or creating backfires, is another process firefighters may employ to stop a wildfire. Literally, this method involves fighting fire with fire. These prescribed—and controlled—fires remove undergrowth, brush, and litter from a forest, depriving an otherwise raging wildfire of fuel.

Benefits of wildfires

Although they are feared, naturally occurring wildfires play an integral role in nature. By burning dead or decaying matter, they can return otherwise trapped nutrients to the soil. They also act as a disinfectant, removing disease-ridden plants and harmful insects from an ecosystem.

Wildfires thin forest canopies and undergrowth, allowing sunlight to reach the forest floor and a new generation of seedlings to grow. In fact, some species of trees, like sequoias, rely on fire for their seeds to even open.

What to do in a wildfire

Before:

  • If you know a wildfire is traveling towards your area, the best thing to do is leave. Immediately.
  • If you live in a fire-prone area, its best to prepare for that course of action ahead of time. Have an evacuation plan in mind and a “go bag” with emergency supplies already packed during fire season.
  • Keep brush, weeds, and other potential fuels trimmed back on your property, especially around your home.
  • Put away grills, propane tanks, or other flammable materials that may be in your yard.
  • Close all doors and windows and fill sinks, tubs, and other containers with water to discourage fire.
  • Shut off natural gas, propane, or fuel oil supplies.
  • When you purchase a home in a wildfire-prone area, try to avoid neighborhoods on steep slopes or barren of vegetation, suggests the California Chaparral Institute. Although some people fear that houses near shrubs are more likely to burn, that’s not necessarily the case, the institute says. Rather, a landscape without vegetation can be the perfect runway for winds to bring embers, which are one of the biggest threats to homes during a wildfire.
  • Wetting your roof may help reduce the risk of airborne embers catching, says the California Chaparral Institute. In fact, some people in fire-prone areas even install rooftop sprinklers for that purpose.
  • If you cannot leave as a fire approaches, dial 911. Then don a face mask, or better, an N95 respirator to help reduce smoke and particle inhalation.

During:

  • If you can still leave, leave.
  • Listen for emergency alerts.
  • If you cannot leave, stay inside. Go to the safest building or room, with the lowest smoke levels. Crouch low for the best air. If you don't have a mask breathe through a wet cloth.
  • If you are caught outside, try to find a body of water to crouch in. If you can't, find a depression with the least vegetation and lie low, covering yourself with wet blankets, clothes, or soil if possible.

After:

  • Do not return until instructed to do so.
  • Listen to authorities before drinking water from the area.
  • Avoid items that are hot, smoky, or charred.
  • Text friends and family, but don’t call. Lines may be busy.
  • Wear a dust mask and document property damage.
  • Beware of the risk of flooding, since trees and protective vegetation might have been removed, exposing loose soil.